A microphone is generally used in order to allow lots of people to be able to hear an audio signal. A microphone system converts the audio signal into an electric signal through a microphone, amplifies the electric signal, and outputs the amplified signal through a speaker. That is, the microphone system amplifies and outputs a low-level audio signal that a user speaks such that many people in a large area can hear it.
The microphone is divided into wired and wireless modes. A wired mode microphone system is constructed in a manner that a microphone and an amplifier are connected through a connection line to input a audio signal outputted from the microphone to the amplifier via the connection line. This is simple in configuration but its user's movement is restricted by the connection line. In case of a wireless mode microphone system, its user can carry only a microphone and a transmitter so that the user can move freely. Accordingly, the wireless microphone is widely used for a stage performance, a lecture, etc.
The wireless microphone market is not activated yet. The market is built up with general industrial wireless microphone products as the main axis. As a microphone used for broadcast and performance, imported products are mainly employed. Especially, the wireless microphone requires accumulation of technical know-how. So medium and small enterprises cannot start positive technical development.
The wireless microphone technique is developed in such a manner that it continuously improves audio quality and simultaneously increases the number of users, and solves problems in frequency policy. With problems related with frequency, especially, ISM band of 2.4 GHz has been explored as a solution to the problem. In addition, a method of applying spread spectrum in consideration of digital transmission and noise problem has been also explored. Korean Patent Appln. 10-1999-0021676 of the inventor, entitled “Recording and decording system of wireless microphone”, discloses a wireless microphone system to which the spread spectrum technique is applied.
Meanwhile, compression techniques for audio transmission have been also developed in various ways. Korean Patent Appln. 10-1999-0021675, entitled “wireless microphone”, of the inventor also discloses a method of converting an audio signal into an MP3 form and transmitting the MP3 signal as a compression technique for audio transmission. However, this patent does not propose a fast optimization technique for converting audio data at a level required for the wireless microphone into MP3 audio signals.
The wireless microphone system needs the fast optimization technique because an MP3 encoder used for an MP3 player is not suitable for the wireless microphone.
A general MP3 player does not require real-time processing in encoding and decoding. That is, audio signals are temporarily stored after encoding and then decoded after a lapse of a predetermined period of time from the encoding in the MP3 player in most cases. This does not need rapid encoding and decoding. Accordingly, the MP3 encoder and decoder used for the conventional MP3 player cannot be applied to the wireless microphone system that requires real-time encoding and decoding.